This proposal addresses three interrelated aspects of the involvement of immunological factors in the pathogenesis of scleroderma. First, we will isolate, purify and characterize the skin antigen to which lymphocytes of patients with scleroderma respond in vitro by releasing soluble mediators (LIF). The purified skin antigen will be used for determining sensitization among patients with scleroderma, CREST syndrome and other connective tissue diseases. It will also be used in studies of the mechanisms through which the hyperreactivity of lymphocytes to the antigen present in normal and scleroderma skin results in lesions characteristic of scleroderma. Second, the contribution of lymphokines released by lymphocytes activated by the skin antigen to the amplification of pathogenic processes will be evaluated. We will look for increased levels of these lymphokines in lymph draining the areas of skin designs in patients with scleroderma. Biologic assays will be LIF and blastogenesis of lymphocytes. In addition, we will study the effects of lymphokines in lymph and in supernatants of lymphocytes responsive in vitro to the skin antigen on the synthesis of collagen by cultured scleroderma fibroblasts. Third, patients with scleroderma will be studied by the mixed lymphocyte culture technique for HLA-D determinants and will be typed for DR antigens to evluate the role of immunogenetic factors in the pathogenesis of scleroderma. The ability of patient's lymphocytes to respond in vitro to the skin antigen will be correlated with the genetic determinants at the D and DR loci of the major histocompatibility complex. These studies will provide an insight into the nature and interactions of different immunopathologic processes thus opening new possibilities for therapeutic intervention and better management of patients.